This invention relates to circuitry for high-speed serial data communication, and more particularly to such circuitry that can switch very quickly from one data rate to another different data rate.
Some emerging high-speed serial data communication protocols (e.g., industry standards) call for circuitry that is able to switch very rapidly from communication at one data rate to communication at another different data rate. For example, the industry standard known as PCI Express Generation 2 (“PCIE Gen 2”) requires circuitry that can switch very rapidly from 2.5 giga-bits per second (“2.5 GBPS”) to 5.0 giga-bits per second (“5 GBPS”), and vice-versa. In order to support such multi-data-rate signalling, both transmitter circuitry and receiver circuitry with this capability is needed. In some instances, an integrated circuit (such as a programmable logic device (“PLD”)) may be provided with both transmitter and receiver components so that the IC can be used as either a transmitter, a receiver, or both. A device with both transmitter and receiver capabilities may be referred to as a transceiver.